: The investigators propose the development and commercialization of a new labeling product exploiting Plasmon Resonant Particles (PRP), which may provide single cell resolution and long term tracing ability of aerosol distribution. The specific initial application planned is tracing of aerosol deposition for treatment of diseases which make use of aerosol therapy. The initial research and development involves optimizing the Plasmon Resonant colloidal metal nanoparticles, the instrumentation, and the methods of observation so as to enable easy observation of PRPs applied to bronchial tissue. The scattered light from the ultrabright, multicolored, stable and inert PRPs is detected using the specialized optical instrumentation and image processing techniques that are presented in the grant proposal. A more challenging and potentially more valuable goal is to demonstrate that these metal nanoparticles, when properly surface coated, can efficiently penetrate into cells, and thereby be used as therapeutic gene delivery vectors. The verification of the use of Plasmon Resonant particles for persistent labeling of impaction sites of inhaled therapeutics, and the development of kits, reagents and instrumentation for manufacture and sale will be key goals of a subsequent phase II program. PROPOSED COMMERCIAL APPLICATION: We believed that our tracer particles will represent a convenient, non-toxic, inexpensive, and high sensitivity complement to Technetium-99m. We believe that these products will be readily accepted for use by the biomedical community involved in animal and human studies of inhalation therapeutics and in the design of new and improved nebulizers, metered dose, and dry power inhalers.